The question normally does not belong here, but still here's an answer:

Just like in the other canon we have, you could have e.g. a newspaper telling us news from your nation.
You could also start with a factbook though, if you want to give an overview over your nation or people(s) first.
Last but not least, you can also just open a thread, where you start telling a story. Either several short stories of many characters, or one long story about one character divided into different chapters. This roleplay can be open to just yourself or to anyone, who wants to interact with you (and can reasonably do so).

There are many possibilities, probably more than I covered here, but those are the ones coming to my mind rn.
To recap:

- A newspaper
- an overview
or
- an own roleplay/telling a story

All of this could be a good start. If people start getting to know you, cooperations with others will also become much more likely and possible, and thus finding new rp-ideas might be easier too